Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$100.35	13.868%	$114.2665	$114.27	$114.25	$114.30
Purchase #2	$59.27	12.431%	$66.6379	$66.64	$66.65	$66.60
Purchase #3	$231.54	3.173%	$238.8868	$238.89	$238.90	$238.90
Purchase #4	$102.53	7.154%	$109.865	$109.87	$109.85	$109.90
Purchase #5	$206.69	7.664%	$222.5307	$222.53	$222.55	$222.50
Purchase #6	$48.77	11.746%	$54.4985	$54.50	$54.50	$54.50
Purchase #7	$182.74	11.535%	$203.8191	$203.82	$203.80	$203.80
7 purchase totals =	$931.89		$1,010.5045	$1,010.52	$1,010.50	$1,010.50